NASA's Messenger space probe finally sent back its first high-res images of Mercury's dark side, and they're surprisingly sparkling. Mercury's dark side is actually "illuminated obliquely" by the sun. Messenger is giving us our first real view of Mercury's Caloris basin, and may help to solve mysteries like why Mercury has a magnetic field when Venus and Mars don't, and what lurks in its shaded polar regions. Click through for the full image.